The mission of the MS Core is to provide cost effective, state-of-the-art instrumentation and analytical expertise to investigators in the Center for Molecular Toxicology for identification of protein and DNA adducts, biophysical and structural analysis of proteins, and for qualitative and quantitative assays of metabolites in tissues and cells. The MS Core is used extensively by eleven of the Center in Molecular Toxicology investigators. Laboratory personnel assist users in developing analytical methods, assist in experimental design, develop standard operating procedures, maintain quality control records on instrument performance and maintenance history, perform routine assays for investigators and train students and fellows in the theoretical and practical aspects of MS. The Core is run as an open-access facility in which users are expected to prepare their own samples and to operate the instruments if they so desire. Administrative staff monitors the use of the instrument facilities by investigators and prepares reports on utilization. The Core has five triple quadrupole liquid chromatography (LC)/MS instruments, one LC/MS ion trap instrument, an electrospray ionization time-of-flight MS (ESI-TOF), two GC/MS systems, and a matrix-assisted laser desorption ionization (MALDI) mass spectrometer. The MS Core is part of the Vanderbilt University Mass Spectrometry Research Center, a comprehensive research unit located in the Medical School. This facility consists of a Core MS service laboratory and the Proteomics Research Core. In addition to providing routine analytical and MS services via the various Core facilities, investigators can form collaborations to solve analytical and structural problems that require non-routine, cutting edge technology. As newer techniques become better understood, they will be made available to the user community through the Core service laboratory. Thus, the Core satisfies the routine analytical needs of investigators and also makes available new analytical capabilities for research problems demanding more innovative solutions that are beyond the scope of a service laboratory. In addition, a training program on various aspects of MS is offered so users can learn to operate the instruments, design experiments, and interpret analytical results more effectively. Both the Core and Research laboratories were extensively renovated in 1998 and new instrumentation was purchased to provide a state-of-the-art facility. Support for the facility comes from service cores affiliated with eight NIH-funded Program Projects and Research Centers, service fees charged to unaffiliated investigators and direct institutional support form Vanderbilt University.